As oil well technology becomes increasingly complex, the importance of collecting and analyzing downhole data is increasing. Well logging instruments are often used to probe subsurface wellbores to determine well and formation characteristics. Sonic tools are an example of well logging tools that may be used to provide information regarding subsurface acoustic properties that can be used to analyze the formation, well completion, or well production.
Downhole fiber optic sensing has greatly expanded sensing capabilities in oil wells. Fiber optics technology is revolutionizing the sensing capability of the downhole environment. Instead of placing a traditional sensor downhole and sending the data to the surface, the fiber optic cable itself may act as a sensor. With appropriate electronics on the surface, traditional fiber optic cables deployed in an oil well are used to measure vibrations as well as other parameters such as temperature and strain. Vibrations, or equivalently acoustics, are particularly relevant for measuring downhole conditions and monitoring downhole activities.
Of particular interest is a distributed fiber optic sensing technology known as “distributed acoustic sensing” or “DAS” which allows for acoustic detection at periodic locations on the fiber. The typical minimum spatial resolution of current distributed sensing technology allows for acoustic measurements at about every meter or so along the fiber. The length of a fiber optic cable deployed in an oil well can typically be several kilometers long. This means that a distributed acoustic sensor can simultaneously measure acoustics at thousands of locations. The ability to make distributed measurements of acoustic signals is nearly unique among all sensing technologies. The information obtained by acoustic measurements has a number of applications, including, but not limited to, monitoring drilling operations, wellbore interventions, wellbore wireline activities, well completions, reservoir properties, seismic correlations, petrophysics, rock mechanics, and other areas.
A distributed acoustic sensor is often recording acoustic data at a higher rate than any other oil field instrument. This available bandwidth can be used to record the data from other sensors or systems. Additionally, there are almost always available distributed acoustic sensor channels that can be utilized.
During drilling operations or well completion activities, human personnel are often responsible for taking notes. However, during downhole activities that occur rapidly, such as fracturing, it is often difficult to properly record an operator's observations or notes (e.g., data log) in real-time during the drilling operations. The notes are generally recorded in handwritten or typed form. It is often difficult for the operator to provide this handwritten or typed data log along with the recorded information for processing and analysis at a later time. Such problems include, but are not limited to, irregular, unreliable, and incomplete operator documentation concerning the drilling operation. It is also difficult to consolidate data from other sensors into a single data stream. Moreover, various problems may arise due to the lack of synchrony for clocks between recording systems.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and are not exhaustive of the scope of the disclosure.